Spectrum use in a shared spectrum environment is sometimes controlled by a central geo-location “database.” The “database” may be implemented with a server that hosts a spectrum management/allocation engine. The engine identifies channels that are not occupied by an incumbent radio in the current location of a device requesting spectrum and deems those channels available for use by the requesting device. Exemplary channels that may be allocated in this manner are unused digital television channels, also referred to as TV white spaces.
Currently, the methods used for requesting and specifying channel (spectrum) availability in managed wireless ecosystems that employ the use of geo-location “database” technology rely on the notion of a channel map. A channel map provides a list of available channels to a radio that seeks wireless spectrum for conducting wireless communications. A channel map is generated for the current location of the requesting radio device to implement spectrum authorization(s) and usage policies. Some example rules that have been promulgated in the U.S. by the Federal Communications Commission (FCC) to facilitate these methods are summarized below.
Under FCC regulations and by conventional geo-location databases (including those outside the U.S.), the location of the device is essentially treated as a point or coordinate. A channel map for any one location is only valid at the point and within a range of permitted error, which may be only a few meters. As a result, conventional methods of controlling spectrum access can be inefficient, especially for mobile devices that frequently change location or move at high velocities. To obtain an accurate and time-valid channel for the location of the device, the device relies on real-time communications with the central “database” authority that distributes the channels maps. As the device moves and changes location, the channel map must be replaced or updated. Otherwise, the channel map is not valid for a new location of the device.
For instance, an exemplary FCC rule for television band radio devices (TVDBs), as set forth in title 15 of the Code of Federal Regulations (15 C.F.R.) includes 15 C.F.R. §15.711(b), which reads in part: “ . . . If the fixed TVBD is moved to another location or if its stored coordinates become altered, the operator shall re-establish the device's: . . . (ii) Registration with the database based on the device's new coordinates.” A Fixed TVBD must re-register if moved, and movement is constrained by a registration accuracy requirement of ±50 m.
Another exemplary FCC rule includes 15 C.F.R. §15.711(b)(3)(ii), which reads in part: “ . . . A Mode II personal/portable device may load channel availability information for multiple locations around, i.e., in the vicinity of, its current location and use that information in its operation. A Mode II TVBD may use such available channel information to define a geographic area within which it can operate on the same available channels at all locations, for example a Mode II TVBD could calculate a bounded area in which a channel or channels are available at all locations within the area and operate on a mobile basis within that area. A Mode II TVBD using such channel availability information for multiple locations must contact the database again if/when it moves beyond the boundary of the area where the channel availability data is valid, and must access the database daily even if it has not moved beyond that range to verify that the operating channel(s) continue to be available.” Only a Mode II TVBD is allowed to use the area protection defined in 15 C.F.R. §15.711(b)(3)(ii).
As indicated, a radio device operating under these types of regulations is required, at least in certain circumstances, to obtain a channel map of available spectrum (e.g., channels) for the current position of the radio device. This ensures that interference with protected devices and incumbent spectrum users will not occur and adversely affect those devices' dominating spectrum rights within the incumbent users' respective protected areas.
As used herein, the term location refers to a regulation-defined point and surrounding permitted error range area for which a channel map having one set of available channels is valid for a radio device. If the radio device were to move out of the location, the radio device would need a new channel map. As indicated, this may be problematic for devices that are in motion. In some cases, a channel map for a geographic area that contains one set of available channels and is valid for multiple locations could be provided (e.g., under the approach of 15 C.F.R. §15.711(b)(3)(ii)). However, providing a channel map covering plural locations is not always practical or efficient. For instance, the set of available channels common to the entire area may be small. In some cases, such as when the area to be considered is relatively large (e.g., covering more than one metropolitan area), the number of available channels for the entire area may be too small to gain benefit or advantage over obtaining new channel maps every time the device has changed location.